What is dehydration?
Updated By PetymFacts checked against official sources on
Quick answer
Dehydration means a pet's body has lost more water than it has taken in, through heat, panting, vomiting, diarrhoea or illness. Early on the gums turn sticky; then the skin loses its spring and the eyes sink. A mildly dehydrated pet needs water and a watchful eye; a weak, vomiting or collapsing one needs a vet now.
Also called dehydration in dogs, dehydration in cats, fluid loss, dehydrated pet.
Key facts
- At about 4 to 5% dehydration the mouth is only semi-dry and the skin springs back normally; by 6 to 7% the gums are dry and the skin is slightly slow to return. Merck Veterinary Manual
- At 8 to 10% the skin returns slowly, the eyes look sunken and the pulse is fast and weak; at 12% or more the eyes are dull and deeply sunken and the pet may be confused or collapse. Merck Veterinary Manual
- Vomiting, diarrhoea, bleeding, overheating and diabetes are among the causes of fluid loss vets list. Merck Veterinary Manual
- Very thin and elderly pets can have slack skin and sunken eyes even when well hydrated, so the skin test can mislead. Merck Veterinary Manual
- Cats are not good drinkers; wet food, several water stations and a fountain all increase their intake. WSAVA
Why do pets get dehydrated in India?
Heat and stomach upsets cause most cases. A dog loses water every time it pants, and a pet with diarrhoea can lose a lot in hours.
Hot summer afternoons, a walk on hot roads, a power cut that switches off the fan or cooler, or a water bowl knocked over while the family is out can all leave a pet short of water. Dogs cool themselves mainly by panting, which costs water, so heat and exercise together are the classic route to both dehydration and heatstroke.
Illness is the other big cause. Vomiting and diarrhoea, from a food upset or from diseases such as canine parvovirus, empty fluid fast, especially in puppies and kittens. Conditions that make a pet pee more, such as diabetes and kidney disease, also leave it chasing water.
How do vets judge how dehydrated a pet is?
Vets estimate dehydration as a percentage of body weight from what they see and feel. You can learn to check the gums and skin at home, but the percentage is a vet's call.
| Gums and mouth | Skin and eyes | |
|---|---|---|
| About 4 to 5% Merck Veterinary Manual | Semi-dry | Skin springs back normally; eyes moist |
| About 6 to 7% Merck Veterinary Manual | Dry | Skin slightly slow to return; eyes still moist |
| About 8 to 10% Merck Veterinary Manual | Dry | Skin clearly slow; eyes sunken; fast, weak pulse |
| 12% or more Merck Veterinary Manual | Very dry | Skin does not spring back; eyes dull and deeply sunken; may be confused or collapse |
From the Merck Veterinary Manual's guide for vets. Older or very thin pets can look dehydrated when they are not, and very young pets can look fine when they are not.
When does a dehydrated pet need a vet?
If The pet is bright, the gums are only slightly sticky and it drinks when offered water
Move it somewhere cool, offer fresh water in small, frequent amounts, and watch closely. Call your vet if it is not back to normal within a few hours. Merck Veterinary Manual
If The pet keeps vomiting or has diarrhoea, especially a puppy, kitten or senior
Call your vet the same day: it may not be able to keep water down, and the cause needs treating. Merck Veterinary Manual
If The skin stays up when lifted, the eyes look sunken, or the pet is weak or wobbly
Go to a vet now. This level needs fluids given by a vet, usually by drip. Merck Veterinary Manual
If The pet is panting hard, hot to touch, drooling or collapsing in the heat
Treat it as heatstroke: start cooling at once with cool water and moving air, then go straight to a vet. Heatstroke in dogs Merck Veterinary Manual
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Questions owners ask
How can I tell if my dog is dehydrated?
- Touch the gums: they should feel wet and slippery, not sticky or dry. Gently lift the skin over the shoulders; in a well-hydrated dog it falls back at once. Sunken eyes, weakness or a fast, weak pulse mean more serious dehydration and a vet visit now. Older and very thin dogs can be harder to judge.
What should I do if my dog will not drink in the heat?
- Move it somewhere cool, offer fresh, cool water and try a different bowl or running water. Adding water to its food can help. A dog that refuses water for more than a few hours, or is also vomiting, lethargic or panting hard, needs a vet the same day, as heatstroke or illness may be the cause.
Can I give my pet ORS or electrolyte drinks?
- Ask your vet before giving any rehydration solution, sports drink or glucose drink. Some products made for people contain sugar substitutes such as xylitol, which is dangerous to dogs. A pet that needs more than water usually needs a vet to find the cause and, often, fluids given under the skin or by drip.
How do I get my cat to drink more water?
- Cats are not natural drinkers. Feed some wet food, place several water bowls around the home away from the litter tray and food, try a pet water fountain, and keep the water fresh. A cat that suddenly drinks much more than usual should see a vet, as that can be a sign of diabetes or kidney disease.
Keep reading
Related terms
More in health conditions
- ArthritisArthritis, or osteoarthritis, is a long-term joint disease in which worn cartilage lets the joint surfaces rub, causing stiffness, swelling and pain. It is very common in older dogs and cats. It cannot be cured, but pain relief from a vet, a healthy weight, gentle regular exercise and a few home changes keep most pets comfortable for years.
- Bloat (GDV)Bloat, or gastric dilatation-volvulus (GDV), is when a dog's stomach fills with gas and twists on itself, cutting off its blood supply. It mainly affects large and giant deep-chested breeds. Unproductive retching, a swelling belly, drooling and restlessness are the signs. It is a surgical emergency that can kill within hours.
- BOASBOAS, brachycephalic obstructive airway syndrome, is a breathing disorder of flat-faced dogs. Narrow nostrils, an overlong soft palate and a small windpipe block airflow, so affected dogs snore, snort, tire quickly and overheat easily. It is worse in heat, humidity and obesity. Surgery can widen the airway, and a lean weight helps.
- Canine distemperCanine distemper is a serious viral disease of dogs that can attack the skin, airways, gut and nervous system. It spreads in droplets from coughing, sneezing and barking, and through body fluids. There is no specific cure, and some dogs do not survive even with treatment. The D in the DHPPi vaccine prevents it.
- Canine parvovirusCanine parvovirus, or parvo, is a highly contagious virus that attacks a dog's gut and immune system. It spreads through infected faeces, survives a long time in the environment and hits unvaccinated puppies between 6 weeks and 6 months hardest. Vomiting and bloody diarrhoea can kill within days, and it is prevented by the core vaccine.
- Cat fluCat flu is the everyday name for an upper respiratory infection in cats. More than 90% of cases are caused by feline herpesvirus, feline calicivirus or both. Cats sneeze, have runny eyes and nose and may stop eating. Most recovered cats remain carriers, and stress can bring the virus back. Vaccination usually prevents severe disease.
- Cherry eyeCherry eye is when the tear gland inside a dog's third eyelid slips out of place and shows as a smooth, red, cherry-like lump in the inner corner of the eye. It is common in young Bulldogs, Beagles, Shih Tzus and Pugs, and needs a vet, usually for surgery to put the gland back.
- Chronic kidney diseaseChronic kidney disease (CKD) is a slow, lasting loss of kidney function, common in older cats and also seen in older dogs. Early on there are often no signs; later a pet drinks and urinates more, eats less and loses weight. It cannot be cured, but a kidney diet, water and regular checks can slow it.
- Dental diseaseDental disease in pets is mostly periodontal disease: plaque bacteria inflame the gums (gingivitis) and then destroy the tissue and bone holding the teeth (periodontitis). It is the most common disorder vets diagnose in dogs, and very common in cats. Bad breath, tartar and red gums are the early signs. Daily brushing prevents most of it.
- Diabetes in petsDiabetes mellitus is a lifelong condition in which a dog or cat cannot make or use enough insulin, so sugar builds up in the blood. Signs are drinking and peeing more, hunger and weight loss. Most diabetic pets live well on insulin injections given at set times with meals, and some cats go into remission.
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Sources
Each source was opened and read on the date shown. How Petym checks its sources
- Merck Veterinary Manual: The fluid resuscitation plan in animals (full review November 2025) (opens in a new tab)
- WSAVA: Frequently asked questions and myths (Global Nutrition Committee) (opens in a new tab)
- Merck Veterinary Manual: What to do in a dog or cat emergency (opens in a new tab)
- Merck Veterinary Manual: Canine parvovirus infection (opens in a new tab)